ATP

Monomers and polymersCarbohydratesLipidsProteinsEnzymesStructure of DNA and RNADNA replicationATPWaterInorganic ions

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Structure

Adenosine triphosphate (ATP) is an RNA nucleotide derivative consisting of:

An adenine base
A ribose sugar
Three attached phosphate groups.

Assessed diagram:

The structure of ATP.

Function

ATP serves as the primary energy storage molecule in cells due to its unique properties:

It remains within the cell where it is synthesised
It is rapidly hydrolysed
It allows energy to be released quickly
It stores and releases less energy than glucose, making it more manageable for cellular use.

Hydrolysis of ATP

ATP provides energy for numerous cellular processes, including:

Muscle contraction
Protein synthesis
Active transport.

Breakdown and synthesis

The energy stored in ATP is released when it is hydrolysed by the enzyme ATP hydrolase:

ATP + H2O → ADP + Pi

Additionally, ATP can donate a phosphate group to another molecule (which becomes ‘phosphorylated’), causing the molecule to change shape or become more reactive.

ATP is regenerated during cellular respiration and photosynthesis.

In these processes, the energy from glucose is used to phosphorylate ADP (ADP + Pi → ATP + H2O) with the help of the enzyme ATP synthase.

This regeneration is a condensation reaction.

Definitions

Adenine: nucleotide base with the letter code A; pairs with thymine in DNA and uracil in RNA, and forms part of ATP.

ADP (Adenosine diphosphate): a nucleotide derivative formed from a molecule of ribose, a molecule of adenine and two phosphate groups. Bonds with a third phosphate group to form ATP.

ATP (adenosine triphosphate): a nucleotide derivative formed from a molecule of ribose, a molecule of adenine and three phosphate groups.

ATP hydrolase: enzyme that catalyses the breakdown of ATP into ADP and Pi, releasing energy.

ATP synthase: enzyme that catalyses the formation of ATP from ADP and Pi. Found in the thylakoid membrane of a chloroplast, and inner mitochondrial membrane.

Hydrolysis reaction: breaks a chemical bond between two molecules and involves the use of a water molecule.

Nucleotide derivative: molecule synthesised from a nucleotide e.g. ATP or cAMP.

Phosphate: ionic molecule made up of PO4-. Found naturally in sedimentary rocks, and dissolved in water sources. Forms part of phospholipids and nucleotides.

Phosphorylation: the addition of a phosphate group to another molecule, often activating or causing a change in shape of the molecule.

Ribose: pentose sugar found in RNA.

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